We anticipate continuing our kinematic studies of the displacement patterns of walking of patients with specific arthritic, neurological and orthopedic disabilities involving primarily the lower limbs. We also plan to measure the nature and amount of assistance (force) required from canes and crutches during walking. We plan to test the patients before and after specific treatment procedures (this year primarily total joint replacements). In order to assess the nature and amount of change in walking performance, the patients' measurements will be compared with standards of normal walking which we have previously established. We also plan to study mechanisms which are operable in causing gait abnormalities. In conjunction with the studies of patients with orthopedic and arthritic disabilities, we hope to evaluate the effect of muscle weakness, joint immobility, abnormal weight bearing during standing, and selected components of their roentgenographic evaluations on their walking performance. We hope to continue studying the effect of muscle spasticity and rigidity and postural steadiness and upright stability on the functional performance of patients with selected neurological disabilities.